Cylinder head and combustion chamber construction



P. E. MACK Dec. 17, 1935.

CYLINDER HEAD AND COMBUSTION CHAMBER'CONSTRUCTION Filed Jan. 31, 1934 FErryE' Mzk 2 -Paten@d 17, 1935 UNITED STATES PATENT oFFica CYLINDER; HEAD AND COMBUSTION v CHAMBER CONSTRUCTION Perry E. .Mack, Milwaukee, Wis., assignor to Briggs & Stratton Corporation, .Milwaukee, Wis., a corporation of Delaware Application January 31, 1934, Serlal.No. 709,168

3 Claims. (Cl. 123-191) This invention relates to new and useful improvements in combustion chamber construction for internal combustion engines and refers more particularly to combustion chambers for L-head "4i en ines. g

It isanobject of this inventionto provide a combustion chamber construction conducive to the elimination or at least substantial diminution of the phenomenon known as detonation and its objectionable consequences. I

While the exact cause of detonation has not been definitely established, several theories having been advanced, it is known that detonation is always accompanied by sudden abnormal. 19' pressure increases in the combustion chamber.

The cause of the sudden abnormal increase in. the gaseous pressure is not entirely understood, but one theory explains this sudden increase in gaseous pressure where fast burning fuels are used, by reasoning that the abnormal rate of flame propagation isthe primary factor-responplace and an explosion wave is set up which 35 strikes the walls .s'of the cylinder and combus tion chamber with a hammer-like blow.

It also has the effect of compressing and still further raising the temperature of the portion first ignited. As a result, the walls of the combustion chamber and the spark plugs or other partially insulated objects in the immediate vi- I cinlty have their temperature raised tremendously so that these elements often form hot spots which cause pre-ignition.

This theory explaining the phenomenon of detonation appears tenable and from this, it may be deduced that by simultaneously igniting the compressed charge at several points rather than at asingle point, the pressure within the combus- 50 tion chamber arising from accelerating flame propagation, may be kept sufliciently low to preelude or at least reduce detonation to an unobjectionable minimum. This has been done in the past through the use of multiple spark plugs, but the present invention contemplates substan-- tially simultaneous ignition of the compressed charge at a plurality of points without entailing the need for multiplev ignition points or spark plugs. The invention accomplishes its purpose by a novel construction of the combustion chamber so that the flame ignited by the spark of a single spark plug shoots through the entire charge at a very high velocity to ignite large areas of the charge substantially, simultaneously.

More specifically; this invention contemplates, as an object, the provision of a combustion chamber construction so designed that initial ignition takes place at an isolated portion of the charge of combustible mixture, which upon ignition is violently projected into charge proper, or in other words, is shot out into the charge proper to substantially simultaneously ignite a large portion thereof.

A further object of this invention is to pro- 29 vide agcylinder head so constructed as to substantially isolate the spark plug from the excessively hot parts of the cylinder head and thereby avoid objectionable overheating of the plug.

With the above and other objects in view which will appear as the description proceeds, my invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the herein disclosed invention may be a made as come within the scope of the claims.

In the accompanying drawing, 1 have illustrated one complete example of the physical embodiment of my invention constructed according 'to the best mode I have so far devised for the practical application of the principles thereof, and in which:

Figure .1 is a cross sectional view through the 40 upper part of an internal combustion engine having a combustion chamber constructed in accordance with this invention; and

Figure 2 is a bottom plan view of the cylinder head in\ which the combustion chamber is formed.

\ Referring now more particularly to the-ac-, companying drawing, in which like numerals indicate like parts, the numeral! designates the cylinder block of a conventional air cooled L- head internal combustion engine having 8. cylinder bore 6 and an intake port I. The cylinder bore 6 and the intakeport I open to the top surface of the cylinder block and communicate with a combustion chamber 8 formed by a cavity It in the underside of a cylinder head 9. The cylinder head 9 is secured to the cylinder block 5 by cap screws I0, and has ,a fluid tight joint l5 around the periphery of the combustion chamber. A piston ll reciprocates within the cylinder bore 6 in the customary manner, and an intake valve I? is provided to open and close the intake port. An exhaust port I2 is, of course, also provided but for clearness, this has not been shown. Its location, which is directly opposite and in line with the intake port, is indicated in Figure 2.

The wall of the cylinder head is preferably cored out to provide air passages l3 extending across its top and communicating with air spaces It at the sides of the cylinder block through which a flow of cooling air is induced.

The cavity IS in the underside of the cylinder head has a horizontal shape, as illustrated in Figure 2, with a portion l6 co-extensive with substantially one-half of the cross sectional area of the cylinder bore and disposed directly thereover. This portion l6 of the cavity is shallow and its upper wall is flat and horizontal. From the portion IS, the cavity extends laterally beyond the cylinder bore to overlie thegintake and exhaust ports as is customary in an L-head engine, and its sides extend in straight parallel lines tangent to the sides of the portion it which, as stated,'are co-extensive with the diameter of, the cylinder bore.

The top wall of the cavity recedes from the edge of the portion It as at H to provide a central combustion chamber portion of progressively and gradually changing depth. This medial portion extends from the edge of the shallow portion It to a point substantially directly above the edge of the bore 6 nearest the valves. Thelaterally extended portion l8 of the combustion chamber from this point on across to its termination adjacent the valves, is of maximum depth and its top wall is horizontal and parallel to the top wall of the portion It.

The combustion chamber thus has its portion of maximum depth directly above the valves and from which the depth of the chamber is grad-' ually decreased-to a point medially over the cylinder from which it continues with a minimum uniform depth.

Communicating with the combustion chamber portion ll of greatest depth there is a spark plug port indicated generally by the numeral l9 and in which a conventional spark plug 20 is secured. The axis of the port I! is inclined with respect to the horizontal to lie substantially in a plane which is tangent to or passes-close to of the port, directly into the combustion chamber. The spark plug closes the pocket 23 and its electrodes 24 are disposed therein.

Hence, it will be seen that when a charge of-- 'combustiblemixture is compressed within the combustion chamber, a, portion thereof is stored .in the ignition pocket or chamber 23. This compressed mixture, upon ignition by the firing of the spark plug, is shot outwardly through the restricted bore 22 with great velocity into the combustion chamber proper, passing substantially entirely across the entire chamber considerably in advance of the flame propagation inltiated at the mouth H of the port. Consequently, the charge is ignited not only at the mouth 2|, 5 but almost simultaneously all along the path of the flame shot out from the mouth. In this manner, the building up of excessive pressures by accelerating flame propagation, is precluded and consequently, detonation eliminated, or at 10 least minimized to a great extent.

With the elimination of detonation, or its diminution to the extent efiected by this invention, it is, of course, possible to use lower grade fuels in the present high compression engines 15 without incurring the heretofore objectionable effects of detonation, which are recognized as overheating and consequent loss of output.

Another important feature of the invention is that the spark plug is located at a comparatively 2o from the hot cylinder head wall. In fact,,the.z5 I

boss into which the spark plug is threaded forms part of the cooling'means with which the cylinder head is equipped to carry off the heat from theextremely hot portions thereof.

By mounting the spark plug in a boss dis-3e; posed in a cool part of the cylinder head and connecting the same to the combustion chamber: by a narrow passageway, the spark plug is sub-.- stantially isolated from the extremely hot portions of the cylinder head and objectionable 3c;- heating of said spark plug is precluded. 7

What I claim as my invention is: v f

1. In an internal combustion engine having a cylinder with a piston operating therein andan intake valve, portions forming a combustion,

chamber over the cylinder and said valve, said combustion chamber having a maximum depth at its portion over the valve and a minimum depth at its portion over the cylinder with an, inclined ceiling joining the said combustion uchamber portions, and an end wall forming one, wall of the portion of maximum depth and hav-* ing an igniting jet port therein whose axis isinclined in correspondence to the inclination oi!v the inclined ceilingn a 2. In an internal combustion engine having a cylinder with a piston operating therein and an' intake yalve, a cylinder head disposed over the cylinder and valve and having a portion of maxi-- mum depth over the valve and a portion of mini- 5g.

.mum depth over the cylinder joined by an in-;

clined ceiling, the portion of minimum depth having a semi-circular side wall to form substantially a continuation of the cylinder wall,:

and the portion of maximum depth having 00.

straight side walls which continue along the inclined ceiling and are tangent to the semi-circuw 18.! side wall of the portion of minimum depth, and said cylinder head having an igniting jet port which opens into the portion of maximum depth adjacent one side wall thereof and whose axis is inclined in correspondence to the incline-- tion of the inclined ceiling so that igniting flame projectedinto the combustion chamber through said jet port swirls, into the combustion chamber substantially tangentially tothe ceiling and sub;

stantially tangentially to the semi-circular side wall of the portion of minimum depth over the' cylinder. Y

3. In an internal combustion en ine having a cylinder with a piston reciprocating therein, and

an intake valve, portions forming a combustion 7 depth at its portion over the cylinder with an chamber por wall of the portion of maximum p having an igniting Jet port therein poin toward the combustion chamber portion of mini- 3 mum depth.

PERRY 2 m 

